The invention relates to a radiation-emitting semiconductor diode comprising a semiconductor body with a semiconductor substrate of a first conductivity type on which are present at least in that order a first cladding layer of the first conductivity type, an active layer, and a second cladding layer of a second conductivity type, the active layer and the cladding layers each comprising a mixed crystal of III-V semiconductor materials, while atoms of different elements are present on at least one sublattice.
Such radiation-emitting diodes, in particular when they are constructed as lasers and when the emission wavelength is in the visible part of the spectrum, are suitable radiation sources for various applications: laser printers, optical disc systems such as Compact Disc (Video) and Digital Optical Recorders, and bar code readers. There are also numerous applications for diodes constructed as LEDs.
Such a radiation-emitting diode and such a method of manufacturing it are known from the article "AlGaInP Double Heterostructure Visible-Light Laser Diodes with a GaInP Active Layer Grown by Metalorganic Vapour Phase Epitaxy" by K. Kobayashi et al., published in IEEE Journal of Quantum Electronics, vol. QE-23, no. Jun. 6, 1987, p. 704. This describes a radiation-emitting semiconductor diode in which an active layer is present between two cladding layers on a substrate of n-GaAs. The active layer and the cladding layers each comprise a mixed crystal of III-V semiconductor materials, here a mixed crystal of InP, AlP and GaP for the cladding layers and of InP and GaP for the active layer, while on at least one sublattice, here the f.c.c. lattice of the III atoms, atoms of different elements are present, here In and Ga atoms for the active layer and In, Ga and Al atoms for the cladding layers. In the radiation-emitting diode, which is constructed as a laser here, there is a strip-shaped region which acts as a resonance cavity and within which electromagnetic radiation can be generated in the active InGaP layer in the case of current passage in the forward direction by the pn junction present. The known diode lasers are manufactured at a growing temperature of 700.degree. C. or lower and comprise a buffer layer of GaAs. The emission wavelength is approximately 670 nm (664 to 690 nm). This means that the photoluminescence wavelength is approximately 660 nm, which corresponds to a bandgap of approximately 1.88 eV. Such a wavelength of approximately 670 nm is particularly suitable for several of the applications mentioned above.
A disadvantage of the known semiconductor diode is that its maximum operating temperature is comparatively low. This temperature depends inter alia on the value of the starting current and on the temperature dependence of the starting current. Both should be as low as possible. Typical values for the starting current density of the known diode laser are 3 to 4 kA/cm.sup.2 and a typical value for T.sub.0 (a high T.sub.0 value implies a small temperature dependence) is 90 to 125K. The maximum operating temperature, and thus the usefulness of the known diode, especially the possibility of emitting large powers, is limited by these values.